A developing winter storm threatened to make a mess for air travelers as it moved across the country into the weekend.

The storm was still gathering strength in the Southwest, but it was forecast to spread heavy rain, snow and icy weather as it tracked east across Texas, Oklahoma and the Southeast. By Sunday, heavy snow was expected to develop across parts of the Southeast and mid-Atlantic, with up to a foot possible for parts of North Carolina and Virginia.

The weekend forecast is still coming into focus, but – so far – it appeared that most major hubs were expected to see only rain. The big exception was Charlotte, where several inches of snow were possible on Sunday. That could likely create significant problems at the airport, a hub for American Airlines.

Weekend travelers also should keep an eye on Atlanta. Current forecasts showed the rain-snow line remaining north of the city, but rainy and blustery weather could still affect operations there.

Beyond that, heavy snow was forecast mostly for smaller or mid-sized airports like Asheville, North Carolina, and Roanoke, Virginia. But the impact at those types of airports could be severe, if current forecasts hold. Wintry weather was also possible at airports like Raleigh/Durham and Greensboro in North Carolina and Greenville/Spartanburg in South Carolina.

In Texas, it appeared likely that major hubs in Dallas and Houston were not going to see wintry weather. Travelers may want to keep an eye on Houston, however. Thunderstorms and heavy rain of up to 10 inches were forecast through Saturday, which could create problems at airports there if flooding restricts access to the airports.

So far, three carriers -- Southwest, Delta, United, American and Frontier -- were waiving rebooking charges for the storm.

It was almost certain that other airlines would do the same for airports in the Southeast and mid-Atlantic as forecasts begin to firm up. Delta, Frontier, United and Southwest were likely to expand theirs, too.

For now, Southwest’s waiver covered Thursday and Friday travelers scheduled to fly through five airports in the region: Albuquerque; Amarillo and Lubbock in Texas; and Oklahoma City and Tulsa in Oklahoma. Southwest does not charge change fees, but its waiver allowed flyers at those airports to make one change to their itineraries without paying a recalculated fare.

Delta's storm policy also covered five airports so far, waiving its change fee of $200 or more for Saturday customers flying through Fayetteville/Northwest Arkansas; Fort Smith, Arkansas; Oklahoma City and Tulsa; and Springfield in Missouri. In addition to waiving the change fee, Delta's policy allowed eligible flyers to make one change without paying an updated fare.

At United, a dozen airports were include in its waiver. They stretched from Albuquerque to Salina, Kansas, to Fayetteville/Northwest Arkansas. United customers traveling to those 12 airports on Friday or Saturday were permitted to make one change with no extra fees or new fare.

American's waiver policy covered eight airports (Amarillo; Fayetteville/Northwest Arkansas; Fort Smith; Joplin, Missouri; Springfield, Missouri; Stillwater, Oklahoma; and Tulsa) for travel on Friday and Saturday. Most customers traveling on those days to those airports were eligible to make one change to their itineraries without paying extra.

Frontier's waiver covered Friday and Saturday passengers ticketed to fly through Dallas/Fort Worth; Oklahoma City; Tulsa; Little Rock, Arkansas; and Wichita, Kansas. Its policy also included one fee-free change with no new fare for most customers.